Brandon, if you truly have 105 octane, you could safely run at least 12.5:1 static compression ratio. However, to get any engine to produce 1.45 hp/CI, you will need to have several things work together and be properly matched. It takes at least 270 CFM through the head at the camshaft lift-minus any lash, and the flow must be with the manifold installed. The intake manifold will need to flow at least 340 cfm in each port so it doesn't pull the head flow down. For a 390 style engine to produce that much HP, you will need a head that flows more than 270 cfm on the intake, and continues to gain flow at higher lift than the camshaft. This way the engine can draw on the intake tract according to the rpm capability of the camshaft. Internal friction must be minimalized so that the rotating assembly should only require about 12-15 lb/ft to rotate by hand, and less is better. You will need at least a 750 cfm carburetor, a good header, preferrably 2" primaries, and great ignition system. You will need an oiling system that has at least 6 qt capability, and if the Fox body is used with stock style or aftermarket engine K member, the rear sump pan is required, and that requires a custom pan. Canton supplies the pan for the Fox bodied cars. It is imperative that you balance the assembly.
As to using iron heads, they retain heat better than aluminum, and are prone to detonate because of that, if the timing is not perfect, and the octane corrrect. Aluminum draws the heat away slightly better, and you can usually get away with about 1/2 point more compression than with iron heads. The newer aluminum heads have better combustion chambers IMO, and with minimal port work will meet the target need of 270-280 cfm airflow. To go through a C1 style head, would most likely require guides, hard exhaust seats, competition valve job, new springs, retainers, keepers, valves, hand blending of machine work, milling to get combustion chambers equal, plane the exhaust face for gasket seal, new valve stem seals, and possibly heli-coils in several of the bolt holes. By the time you set up those old heads properly, you will have MORE than a new set of Edelbrocks will cost, and still not make the same amount of power over time. The iron heads will deteriorate under racing, and require valve jobs regularly. It just makes economic sense to start any racing project with the best possible equipment you can afford.
To make an honest 550 HP with a 390 style engine, will require close to $10K and that is a conservative estimate IMO. Hope this helps. Joe-JDC.
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